The present invention relates to apparatus for gasification of finely divided solid or liquid fuels, such as coal.
In gasification of coal, on leaving a gasifier the gas had a temperature at which the ash had a high fluidity, as a rule higher than 1400.degree. C. The emerging gas contained a mist of molten slag particles. For further processing, the crude product gas had to be cooled down to a lower temperature, such as about 300.degree. C. Slag from ash in the coal was usually sticky in the temperature range of from about 1500.degree.-900.degree. C. In this temperature range, difficulties tended to arise due to the tendency of the sticky slag to build up deposits on walls, outlets and the like. The slag deposits interfered with good operation of the gasification equipment, and could even lead to complete blocking of the equipment. Once the particles had cooled to a temperature where they were no longer sticky, they could be removed by known techniques such as cyclones, bend separators, filters and similar devices.
Although sometimes molten contaminants in a gas were so thinly liquid, i.e. non-viscous, that removal of the greater part thereof did not give any problems, as a rule a mist of molten particles remained behind in the gas, which upon cooling temporarily became sticky and then tended to cause the processing difficulties mentioned.
Further, during gasification operations, the very large temperature differences in the gasification apparatus from higher than 1400.degree. C. in the gasification chamber down to a few hundred degrees centigrade in the waste heat boiler gave rise to severe thermal stresses in the various component parts of the apparatus.